A cobalt-chromium-molybdenum (Co—Cr—Mo) metallic alloy specified by ASTM F75 is commonly used for surgical implants such as for prosthetic knees, hips, shoulders, elbows, wrists, ankles, fingers, toes and spinal elements because of the alloy's strength, corrosion resistance, and biocompatibility. This Co—Cr—Mo alloy has greater wear resistance than stainless steels and titanium alloys. The nominal composition of the F75 alloy is 27.00 to 30.00% Cr, 5.00 to 7.00% Mo, 0.35% C maximum, 1.0% Si maximum, 1.0% Mn maximum, 0.50% Ni maximum, 0.75% Fe maximum, 0.010% B maximum, with balance of Co and other inevitable trace elements and impurities. All percentages herein are by weight, unless indicated otherwise.
Welsh et al., Surgical implants: the role of surface porosity in fixation to bone and acrylic. J Bone and Joint Surg Am 53: 963, 1971 and Pilliar et al., Porous surface layered prosthetic devices. Biomed Eng 10:126, 1975, described implants having a porous Co-based alloy coating of gas-atomized spheres on a substrate of the same composition to provide open surface porosity for bony ingrowth. Bobyn et al., The optimum pore size for the fixation of porous-surfaced metal implants by the ingrowth of bone. Clin Orthop 150: 263, 1980, study the impact of distinct surface-coating pore size on fixation of implants.
Rivard et al. U.S. Pat. No. 8,383,187 describe manufacturing a surgical implant by applying aspherical metallic particles to a substrate.
There is need for commercially available coating systems for surgical implants which cost-effectively address the needs for such coatings in terms of porosity, strength, wear-resistance, friction, and manufacturability.